Variable inside returned lambda loses conditional type information

[gwax]

Bug Report

When returning a lambda containing an uncaptured variable, mypy losing conditional information about the type of that variable.

To Reproduce

https://mypy-play.net/?mypy=latest&python=3.11&gist=634d85b9f00175d6b4a1f4929d3ba848

from typing import Callable

def foo(i: int) -> int:
    return i
    
def bar(j: int | None) -> Callable[[], int]:
    if j is not None:
        return lambda: foo(j) # <- error
    return lambda: -1
    
def baz(j: int | None) -> Callable[[], int]:
    if j is not None:
        def inner():
            return foo(j)
        return inner
    return lambda: -1

Expected Behavior

no error for lambda or inner function

Actual Behavior

the returned lambda results in an error

main.py:8: error: Argument 1 to "foo" has incompatible type "Optional[int]"; expected "int"  [arg-type]

Your Environment

• Mypy version used: 1.1.1 (mypy-play)
• Python version used: 3.11 (mypy-play)

[rhithesh]

hey we can use cast(int,j) INSTEAD OF foo(j) I looked it up online.

[erictraut]

This is a duplicate of #2608.

You can work around this limitation by assigning the narrowed value to a temporary variable.

def bar(j: int | None) -> Callable[[], int]:
    if j is not None:
        j2 = j
        return lambda: foo(j2)
    return lambda: -1

[eltoder]

@erictraut @AlexWaygood #2608 is closed as done, but this examples still fails. Also note that using a nested def works, only lambdas are affected. Maybe there's a separate bug with lambdas?